At 1,400 miles in length, the Great Barrier Reef is the largest living structure on our planet and consists of more than 600 types of hard and soft corals. Thousands of varieties of fish and molluscs call this breathtaking maze home. And if that isn’t enough to impress you: the Great Barrier Reef is so massive it can be seen from outer space. Yes…outer space! Needless to say, visiting this special place has been on my bucket list since I was a kid and saw my first film chronicling the explorations of Jacques Cousteau and the crew of the Calypso.

It was spectacular. I shared turquoise blue waters with blacktip reef and tawny nurse sharks, took flight with white-spotted eagle rays, and floated quietly in the presence of loggerhead sea turtles. Best of all, I got to rub elbows with the folks who make the GBRMP possible. And I learned that they spend a lot of time thinking about the same issues as we do: education and outreach, partnerships and local engagement, long-term monitoring, and best practices for enforcement.

Because the Great Barrier Reef is a single, complicated structure with trillions of delicately balanced living and breathing components, it is also ground zero for our increasingly warm and more acidic ocean. What happens to the sensitive, exposed habitats of the Great Barrier Reef in the next couple of years may be a harbinger of what’s to come in the rest of our ocean in the coming decades.

Heron Island, where I spent much of my time, is a coral island that sits directly on the Reef, just north of Gladstone, Queensland, Australia, where the world’s fourth largest coal export terminal is located. The Island is home to nesting green sea turtles, giant shovel-nosed rays, and a 400-pound Queensland grouper named “Gus.” It’s also home to the University of Queensland Research Station, where scientists are studying the effects of carbon emissions and warmer temperatures on local corals.

These scientists know that the fossil fuels we are burning—like coal—don’t just go into the atmosphere; they are also absorbed by the ocean. When this carbon pollution is absorbed by seawater, it turns it more acidic. In fact, the ocean is 30% more acidic today than it was 150 years ago. And increasingly acidic water is bad news for animals that build shells, including corals.

Warming waters, also as a result of carbon dioxide, mean more bleaching and more algae and diseases that corals have to recover from. Scientists in the Great Barrier Reef are looking at what this all will mean for the Reef and for the ocean as a whole.

While the situation is very concerning, it’s my hope that our global community will be able to significantly reduce carbon pollution and ocean acidification to keep our ocean—and the wonders that reside within it— healthy.

How much do you know about the waters that cover 70 percent of Earth’s surface and the creatures that call it home? Test your ocean knowledge with our short quiz.

Study these five questions and see how much you know:

What is the largest living structure on Earth?

How did bull sharks receive their name?

What is the biggest fish in the ocean?

What is the most venomous marine animal?

How are polar bears able to walk on ice?

Stumped? Click the link below to see the answers.

What’s the largest living structure on Earth?

The Great Barrier Reef. This stunning Australian wonder, visible from space, is composed of nearly 3,000 individual reefs and stretches for 1,600 miles.

How did bull sharks receive their name?

Bull sharks have a reputation for being fighters. This characteristic, accompanied by their short and blunt snouts, helped them gain the name “bull shark.”

What is the biggest fish in the ocean?

The whale shark. They can grow to be up to 50 feet long and weigh as much as 40 tons. These gentle giants eat mostly floating organisms that they strain from the water through their 3-feet-wide mouths as they swim.

What is the most venomous marine animal?

The Australian box jellyfish. The venom of these highly advanced predators, often called sea wasps, contains toxins that attack the heart, nervous system and skin cells. Their tentacles can reach 10 feet in length with body sizes reaching up to 1 foot in diameter.

How are polar bears able to walk on ice?

The rough pads and fur of a polar bear’s large paws help it grip the ice more easily and avoid slipping when walking on it.